ATVS-UAM System Description for the Audio Segmenta

FALA 2010
VI Jornadas en Tecnología del Habla and II Iberian SLTech Workshop
ATVS-UAM System Description for the Audio Segmentation and Speaker
Diarization Albayzin 2010 Evaluation
Javier Franco-Pedroso, Ignacio Lopez-Moreno, Doroteo T. Toledano, and Joaquin GonzalezRodriguez
ATVS Biometric Recognition Group, Universidad Autonoma de Madrid, Spain
{javier.franco, ignacio.lopez, doroteo.torre, joaquin.gonzalez}@uam.es
structure of the speech, such as Shifted Delta Cepstral
coefficients (SDC) [5] and the usage of Maximum Mutual
Information (MMI) [6] to improve the discrimination rate
while maximizing the mutual information between acoustic
classes. In multi-class problems such as Language
Recognition or even Speech Recognition, GMM-MMI and
HMM-MMI models have shown notable discrimination
improvements, also motivating their usage for this submission.
The rest of the paper is organized as follows. Section 2
describes feature extraction for each system. Then, we
describe system details for each evaluation task, audio
segmentation (Section 3) and speaker diarization (Section 4).
Finally, conclusions are presented in Section 5.
Abstract
This paper describes the ATVS-UAM systems submitted to
the Audio Segmentation and Speaker Diarization Albayzin
2010 Evaluation. The ATVS-UAM audio segmentation
system is based on a 5-GMM-MMI-state HMM model.
Testing utterances are aligned with the model by means of the
Viterbi algorithm. Spurious changes in the state sequence were
removed by mode-filtering step. Finally, too sort segments
were removed. The ATVS-UAM speaker diarization system is
a novelty approach based on the cosine distance clustering of
the Total Variability speech factors -the so-called iVectorsperformed in two steps, followed by a Viterbi decodification
of the probabilities based on the distances between the
candidate speaker centroids and the iVectors stream.
2.
2.1.
Index Terms: audio segmentation, speaker diarization,
viterbi, factor analysis, maximum mutual information.
1.
Feature extraction
Audio segmentation
Audio Segmentation parameterization consists in 7 MFCC
with CMN-Rasta-Warping concatenated to their 7-1-3-7
Shifted Delta Coefficients (SDC).
SDC features have been widely used in Language
Recognition due to the fact that they capture the time
dependency structure of the language better than the speed or
acceleration coefficients (also known as delta and delta-delta).
Similarly, SDC features are expected to distinguish the time
dependency of the speech over the music or noise.
Introduction
In the recent years the speaker and language recognition
community dedicates special attention to the real conditions
challenge. This challenge involves audio recordings preceding
from different sources in addition a single speaker, such as
noise, channel effects, speech or music. Speaker turns in a
conversation also causes significant degradation in
performance for poor segmentations. Such challenge
motivates the ATVS-UAM participation in Albayzin 2010.
Recently, Factor Analysis (FA) methods have shown excellent
results facing some of these problems such as the
compensation of the channel and speaker variability.
Moreover, FA is currently the state-of-the-art technology for
speaker and language recognition, with promising results in
other fields such as speech recognition. A successfully FA
scheme for speaker diarization was firstly proposed by
Castalado [1] in 2008 and later extended in [2]. Castaldo uses
low dimensional speaker vectors that are obtained over highly
overlapped windows of one-second length. Thus FA
generalizes as a secondary parameterization of the input
speech stream. This new short-term speaker-factors space
shows excellent results when classical speaker diarization
techniques are applied on it. In [3] Najim and Kenny enhances
the classical FA scheme by: a) Modeling together speaker and
channel variability, in what is called total variability.
Additional improvements can be achieved with a
discriminative training of the target classes such as Linear
Discriminant Analysis (LDA) [4] and b) Estimating the
posterior probabilities of a speaker participating in the
conversation as the cosine distance between the averaged
iVectors over the training and testing utterances [4].
Other concerns that have been addressed during the design
of the ATVS-UAM Audio Segmentation System were the use
of features that includes information of the time dependency
2.2.
Speaker diarization
The front-end parameterization for speaker diarization is
illustrated in the Figure 1. It follows a classical Speaker
Recognition recipe: 19 MFCC coefficients concatenated to
their deltas and followed by Cepstral Mean Normalization
(CMN), RASTA filtering and feature warping.
All the training data labelled as ‘speech’, ‘speech with
noise in background’ and ‘speech with music in background’
is used to train a 1024-mixtures UBM model. Given this
UBM, sufficient stats are extracted for every labeled segment.
The total variability subspace is then modeled following the
FA recipe. The next step is to compute a LDA matrix that
discriminates among speakers. Such matrix is trained with the
speaker labels provided and compensated statistics, called
iVectors.
Figure 1: Schematic diagram of the feature extraction
scheme for speaker diarization.
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overlaped-. Compensated iVectors in each slice are clusterized
based on their cosine distance. The number of clusters is
controlled by maximum allowed distance between the vectors
to the centroid of the cluster. In our implementation we used
as centroid the averaged vector in each cluster and it
represents a candidate speakers model. Candidate speaker
models are accumulated over all the slices in the test session,
together with the frequency of appearance of their cluster.
Since speakers are expected to appear in more than one slice, a
secondary clustering is used to merge the first iteration
centroids, obtaining then an enhanced set of candidate
speakers. A prior probability is assigned to each of the
candidate speakers based on its relative frequency of
appearance in the entire session.
In a second pass over the slices we compute the
probability of each candidate speaker with the stream of
iVectors. Such probability is estimated using the cosine
distance and normalized with the prior probability of each
candidate speaker. The final diarization labels are obtained
with a Viterbi decodification of these scores.
As in [1] our back-end parameterization computes
iVectors every 20ms over a one second length window.
Resulting iVectors are projected over the space defined by the
LDA matrix.
3.
Audio segmentation system
The ATVS-UAM-UAM audio segmentation system is
illustrated in the Figure 2. It is based on the Viterbi alignment
of the audio stream using a five-state HMM. One for each
target acoustic class: ‘speech’, ‘speech with noise in
background’, ‘speech with music in background’ ‘music’ and
‘others’.
Figure 2: Schematic diagram of the ATVS-UAM audio
segmentation system
Each HMM state consists in a 1024 mixtures GMM,
previously trained by means of 5 iterations of the MaximumLikelihood criterion, and enhanced later by means of 18
iterations of the Maximum Mutual Information criterion. This
latter step were carried out using the HMM Toolkit STK
software from BUT [email protected] (Brno University of
Technology, Faculty of Information Technology) [7]. All
development data provided for the evaluation were used to
train these GMMs and no additional data were used.
The SDC features stream is previously divided into 60
seconds length audio slices that are independently processed.
Initial 2 seconds of each slice are overlapped with the previous
one.
Viterbi alignment is performed using the HMM Toolbox
for Matlab by Kevin Murphy [8].
After the Viterbi decodification, a mode-filtering step over
a 700 ms sliding window is used to avoid spurious changes
between states. Finally, for each class, very short segments
were removed –those ones with length smaller than around 3
seconds.
Table 1 summarizes ATVS-UAM audio segmentation
system testing timing.
Figure 3.Schematic diagram of the ATVS-UAM speaker
diarization system.
Table 2 summarizes ATVS-UAM speaker diarization
system testing timing.
Table 2: Breakdown timing for ATVS-UAM speaker
diarization system.
Testing (per 4 hours session file)
Feature extraction
40 minutes
iVectors computation
32 hours
iVectors clustering + Viterbi 15 minutes
decodification
5.
This paper summarizes the ATVS-UAM participation in
Albayzin 2010 Evaluations. ATVS-UAM submits results for
two of the four proposed evaluations: Audio Segementation
and Speaker Diarization. In the latest case we present a
novelty approach based on FA to model the total variability
subspace. The so-computed iVectors are clustered based on an
estimation of the likelihood using cosine distance. Thus,
centroids to each cluster can be considered candidate speakers.
Likelihoods for each candidate speakers are computed in a
second pass over the iVector stream. The final sequence of
decisions is computed using the Viterbi algorithm. The ATVSUAM Audio Segmentation system submitted is based on a
five states HMM, each of them trained independently with a
1024 gaussians GMM using MMI. The final sequence of
decisions is obtained as an enhanced Viterbi decodification.
Table 1: Breakdown timing for ATVS-UAM audio
segmentation system.
Testing (per 4 hours session file)
Feature extraction
14 minutes
Viterbi decodification + 20 hours
mode-filtering
4.
Conclusions
Speaker diarization system
ATVS-UAM speaker diarization system (Figure 3) is based on
the previous works [2] and [3].
The MFCC features stream is firstly divided into 90
seconds length audio slices –contiguous windows are 33%
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6.
[1]
[2]
[3]
References
[4]
F. Castaldo, D. Colibro, E. Dalmasso, P. Laface, and C. Vair,
“Stream-based Speaker Segmentation Using Speaker Factors
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2008, pp. 4133 – 4136.
P. Kenny, D. Reynolds, F. Castaldo “Diarization on Telephone
Conversation using Factor Analysis”. IEEE Journal on Selected
Topics In Signal Processing. 2010.
Najim Dehak, Patrick Kenny, Rda Dehak, Pierre Ouellet, and
Pierre Dumouchel, “Front end Factor Analysis for Speaker
Verification,” IEEE Transactions on Audio, Speech and
Language Processing, 2010.
[5]
[6]
[7]
[8]
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Najim Dehak, Reda Dehak, James Glass, Douglas Reynolds, and
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http://speech.fit.vutbr.cz/
http://www.cs.ubc.ca/~murphyk/Software/HMM/hmm.htm
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